Gas lift apparatus



y 5, 1954 R. P. VINCENT 3,131,644

GAS LIFT APPARATUS Filed Nov. 14, 1960 2 Sheets-Sheet 1 l I?" I3 2| i 44 I I76 72| 7 v 73- H I 3 68 69 a? g Q 1| g Q z RENIC P; VINCENT INVEN TOR.

ATTORNEY M y 5, 1964 R. PAVINCENT 3,131,644

GAS LIFT APPARATUS Filed Nov. 14, 1960 2 Sheets-Sheet 2 RENIC P. VINCENT INVEN TOR.

{a Q E E Z ATTORNEY FIG. 2

United States Patent 3,131,644 GAS LIFT APPARATUS Renic l. Vincent, Tulsa, Okla, assignor t0 Pan American Petroleum Company, Tulsa, Okla, a corporation of Delaware Filed Nov. 14, 1960, Ser. No. 69,045 16 Claims. (Cl. 103232) This invention relates to an improved apparatus for gas lifting a well and, more particularly, ti relates to a means for increasing the lifting efliciency of a continuous gas lift system. This application is a continuation-in-part of my earlier application Serial No. 714,108, filed February 10, 1958, now Patent No. 3,016,844.

In the above application it is pointed out that the lifting gas/produced liquid ratio and the lifting efficiency of a gas lift well, particularly the gas lift well which produces continuously, can be substantially increased by reducing heading or slugging of the liquid near the surface in the producing conduit. Heading, as the term is used therein, refers to the intermittent production from a well of separately detectable slugs of liquid and gas. As the length of a slug of liquid in a gas lift well increases, the longer the slug of gas beneath that slug of liquid must be to lift the liquid. As the length of the gas slug is thus increased, the greater the blow-down of gas following the production of each slug of liquid and, consequently, the greater the loss of energy and the lower the lifting efficiency. This lifting efficiency can be increased by providing a continuous gas lift system in which the lengths of the intermittent slugs of liquid and gas are reduced to a minimum, or the two are so uniformly blended at the top of a well that there is no apparent slugging or heading of the produced fluid.

This increased efficiency can be accomplished by producing short, alternate slugs of liquid and gas in the producing conduit at or near the bottom of a well. That is, by injecting short slugs of the lifting gas intermittently into the liquid in the producing conduit at a rate sutiicient to halt temporarily the flow of liquid into the pro ducing conduit, slippage of liquid in the tubing or other producing conduits can be substantially reduced and the lifting efiiciency can be materially increased.

It is, therefore, an object of this invention to provide an improved gas lift system. It is a more specific object of this invention to provide an apparatus for injecting gas intermittently into a liquid-producing conduit at relatively high frequency for the purpose of increasing the lifting efficiency of the gas. It is a further object of this invention to provide a gas lift valve which will inject periodically, at high frequency, a large volume of gas into the production conduit of a continuous gas lift well. An additional object of this invention is to provide such a gas lift system which operates autimatically without manipulation and without pulsation of the lift gas supplied to the well.

In this description, reference will be made to the accompanying drawings in which:

FIGURE 1 is a cross-sectional view of a part of a well having in combination one embodiment of a gas lift valve adapted to inject large volumes of gas into the production V tubing at a high frequency.

liquid and gas in the production conduit at one time. ,In

3,131,644 Patented May 5, 1964.-

its more particular aspects, this invention is directed to a gas lift valve which will intermittently inject gas into a production conduit at a frequency high enough to provide from about 2 to about 100 or more separate and distinct slugs of liquid in the production conduit at one time. More specifically, this invention relates to a gas life valve of the type disclosed in my original application having improved means for controlling the volume of the gas slugs and the frequency of the injection.

For a more detailed description of the invention, reference will now be made to the drawings. Apparatus suitable for this type of gas lifting is shown in FIGURE 1. In this embodiment, the well is represented by casing 10 which is equipped with a production tubing 13 having a standing valve 15 in its lower end. A packer 16 closes the annular space between the casing and tubing and provides a conduit for lift gas through the annulus 21 from the well head to the gas lift valve assembly 24. A gas injection port 37 in the tubing admits gas from the annular conduit to the tubing via the gas valve assembly 24. The standing valve 15 in the tubing prevents backflow of the fluids from the tubing when high pressure is imposed on the tubing during the injection cycle. A conventional well head installation may be used. Also, one or more gas lift valves, commonly referred to as kickoff valves, may be installed on the production tubing at spaced points to assist in unloading high columns of liquid which might accumulate in the well during closed-in periods.

The gas lift valve assembly 24 shown in FIGURE 1 includes a gas surge chamber 1717 at the top with a pressure-actuated pilot valve 44 inside the surge chamber. The pilot valve controls the flow of gas from the surge chamber to a fluid motor below. The fluid motor operates a three-way valve which diverts lift gas either to the surge chamber or to the production tubing.

The pilot valve 44 is operated by a bellows 48 in housing 46. The housing is open whereby the pressure inside the surge chamber 17' can act on the bellows. A compression spring 45 urges the valve into a position which closes outlet 43 in the surge chamber. Support member 49 anchors the pilot valve assembly in the surge chamber. Perforations 50 in member 49 provide fluid communication between the upper part of the surge chamber 17 and the lower part 17 which houses the pilot valve. The surge chamber is compartmented in this manner to facilitate the adjustment of the operating characteristics of the valve, as discussed later. The bellows 48 can be prepressured with a compressible fluid such as Freon. In some cases it may be desirable to eliminate the spring 45 and rely solely upon the prepressured bellows to close the valve. The bellows collapses to lift the valve 44 off the outlet 43 when the presure inside the surge chamber reaches the opening level. An orifice 22 is provided to meter the gas into the surge chamber at the desired rate.

The fluid motor which operates the three-way valve consists principally of a piston 68 in the housing 29 and a compresison spring 69 urging the piston upward. An

exhaust port 72 through the piston permits gas pressures above and below the piston to equalize whereby the spring 69 is the only force acting on the piston. Accordingly, the normal position of the injection valve member 67 is as shown in FIGURE 1 with the upper face 66 seated against the outlet port 65. The increase in pressure above piston 68 which occurs when the pilot valve opens the outlet 43 in the surge chamber moves the piston down until the lower face 75 of valve member 67 closes outlet 77. In this manner the lift gas flowing through the inlet gas port 62 is diverted from the surge chamber to the production tubing.

The length of time valve 44 remains open depends upon how long it takes the pressure in the surge chamber to vent through exhaust port 72 in the fluid motor and fall to the closing pressure of the bellows-spring assembly. Likewise, the length of time the valve remains closed depends upon the time necessary for the opening pressure level to be reached at the flow caypacity of metering orifice 22. A convenient means for increasing the lengths of both the open and closed periods is to increase the volume of surge chamber 17". Chamber 17 is shown as a removable section above chamber 17' and communieating with the lower chamber via perforations 50 in the pilot valve support member 49. Thus, the desired range of operating cycle can be obtained by using an upper chamber section 17" having the proper volume.

The frequency of the gas injection cycles and the volume of gas injected each cycle which result in the highest efliciency can usually be determined best by trial and error. In most installations it is desirable to have the valves opened and closed from about one to about ten or more times per minute. Observation of the heading or slugging of the fluids reaching the surface can be used as a guide to the optimum adjustment of the valves. The ptiinum frequency of the injection cycles is the frequency at which the surface tubing pressure is low and is substantially uniform or steady. This condition is attained when the alternate slugs of liquid and gas arriving at the surface are so short that the stream is substantially homogeneous. Under this condition, there is no excess gas and, therefore, the well is operating at maximum efliciency. Since a frequency lower than the optimum either will not lift liquid from the well or will lift liquid by heading, it is generally desirable in determining the optimum frequency to try first a high frequency and then decrease the frequency of gas injection until the well is just on the threshold of heading. The frequency of gas injection can thus best be determined by trial and error.

The volume of the chamber 17'17" and the flow capacity of exhaust port 72 determine the length of time the gas injection valve 67 is open. The length of time the injection valve is closed, and the outlet 77 is open admitting gas through line 76 and orifice 22 into chamber 17', is primarily a function of the flow capacity of the orifice 22. The larger the orifice the shorter the time the outlet port 65 is closed and the higher the injection frequency. As mentioned previously, the frequency can also be controlled by varying the volume of the gas surge chamber as well as by other means, such as varying the mean differential pressure across the orifice 22, i.e., by changing the pressure in the gas conduit 21.

In operation, the bottom of the tubing 13 is lowered to a substantial distance below the working or dynamic level of the liquid in the well so that the liquid will rise in the tubing to an elevation above the gas inlet port 37. The packer 16 is set and high-pressure gas injected into the gas conduit 21. The kick-off valves will unload liquids from the tubing until the liquid level reaches a point where gas can be injected at the lower valve. Gas enters the inlet gas chamber 78 through inlet gas port 62, then passes through outlet 77, tube 76 and orifice 22 into surge chamber 17. Perforations in the pilot valve support member 49 provide fluid communication between the upper and lower surge chamber sections 17' and 17". Gas chamber outlet 43 is closed by valve member 44, thus permitting the gas pressure to increase inside the surge chamber. Compression spring 45 urges the valve member in the closed position. Additionally, the high gas pressure acting on the top of the valve and the low tubing pressure on the bottom of the valve tend to hold it in the closed position. The bellows 48 in housing 46 inside chamber 17 is ultimately collapsed when the pressure in the chamber becomes great enough to overcome the force of spring 45 and the pressure differential across valve 44. When this occurs, there is a sudden flow of gas from the surge chamber into chamber 73 producing suflicient pressure therein to move piston 68 and valve member 67 down until the lower chamber outlet 77 is engaged by lower face 75 interrupting the flow of gas through tube 76 into chamber 17'. In this position of valve member 67, the gas flows from conduit 21 through inlet 62 and ports 65 and 37 into the production tubing. This causes the pressure in the tubing to rise rapidly. Desirably, the fluid pressure in the tubing, when the injection valve is open, is greater than the pressure in the well below the standing valve 15, so it closes. This causes the slug of liquid in the tubing above the injection valve to be lifted by the gas. Gas chambers 17', 17" and 73 vent through exhaust port 72 until the force of the spring 45 overcomes the counteracting force of the bellows. At that time, valve 44 closes outlet 43. The pressure in chamber 73 continues to decline as gas flows through opening 72 until the force of spring 69 and pressure drop across port 65 are great enough to move valve member 67 into engagement with port 65, thus stopping the flow of lift gas to the tubing. Simultaneously, outlet 77 is uncovered, permitting the repressuring of chamber 17' to start another cycle in the operation of the valve. During the time that port 65 is closed, the pressure within the production conduit is less than the well pressure below the packer and liquid flows into the lower end of the tubing through the standing valve. This liquid displaces the slugs of gas and liquid above it higher into the production conduit.

The flow capacity of the surge chamber outlet 43 must be greater than that of the exhaust port 72 to maintain suificient pressure above the piston 68 to hold the valve member 67 in the lower position whereby lift gas can flow through port 65.

The gas lift valve may be of the insert or retrievable type so that it can be removed as desired without pulling the tubing. An apparatus of this type is shown in FIG- URE 2. In this embodiment, the assembly can be retrieved with wire line equipment so that adjustments or repairs can be made. A cross-over fitting 25 is placed in the production conduit at the elevation where the retrievable gas lift valve is to be seated. A packer 16 closes the annulus between the tubing and casing below the cross-over fitting. As in the apparatus illustrated in FIG- URE 1, this provides a conduit for the lift gas. This crossover fitting comprises in part an outer shell 26 and a valve seating or inner sleeve 27. The inside diameter of sleeve 27 is smaller than the inside diameter of tubing 13, so that retrievable valves can be easily lowered through the tubing and will seat in the sleeve. The sleeve has means to anchor a retrievable valve in operating position. This may comprise an upper shoulder 28, smaller in diameter than the body 29 of the retrievable valve. The shoulder stops the retrievable gas lift valve 24' in operating position with the inlet gas port 62 at the elevation of an annular recess 31 in the cross-over fitting. This annular recess is in fluid communication with the gas conduit 21 through the radial gas inlet 32 in the outer shell 26. Gas can thus flow from the gas conduit in the annular space between the casing 10 and the tubing 13 by way of the cross-over gas inlet 32 and the gas valve inlet port 62 into inlet gas chamber 78. In some cases, it is desirable to lock the retrievable valve in this operating position. In one embodiment of such a lock, a spring latch 33 is connected to the lower end of valve body 29. Tapered catches 34 on the lower end of the cantilever springs 35 cooperate with a lower shoulder 36 in sleeve 27 to hold the retrievable valve down in this operating position against the force of the well fluids rising in the tubing. However, due to the taper either on the catches as shown or on the lower shoulder, the retrievable valve can be unseated and removed from the tubing by use of an overshot fishing tool which engages knob 51 and exerts a force greater than the force of the well fluids. Since the retrievable operating valve fills the inner sleeve 27, a fluid by-pass through fluid inlet port 40, annular passage 38,

are spaced above and below the annular recess 31, re-

spectively, when the valve is in operating position to seal the space between the valve body and the inner sleeve 27 of the cross-over fitting 25. Thus, the well fluids entering the tubing through standing valve 15 pass upwardly through the annular passage 38 around the valve body 29 and into the annular space 54 between the gas chamber 17-17" and the tubing. The flow of gas through the outlet port 65 in the valve body and the gas injection port 37 in the inner sleeve of the cross-over fitting into the production conduit is controlled by slide valve 57.

Normally, this slide valve is closed by the compression spring 69, acting against the lower end of rod 56, which carries the slide valve. A sleeve valve 58 is also carried by the rod 56. This valve slides along tube 76 to open and close chamber outlet 77 at the lower end of the tube. In this manner, gas from the inlet gas chamber 7 8 flows into either the tube 76 and orifice 22, or the outlet port 65 and gas injection port 37, depending upon whether the rod 56 is in the upper or lower position. Web members 74 join the slide valve 57 and sleeve valve 58 to the rod 56, thus providing substantially unrestricted gas flow from the bottom to the top of the inlet gas chamber. A bellows 55 attached to the gas chamber head 59 positions the rod 56 in response to the pressure inside gas chamber 73. In this arrangement, high-pressure gas which discharges from gas surge chamber I717" through outlet 43 into chamber 73 causes the bellows 55 to collapse and move the slide valve 57 downward, uncovering outlet port 65. Simultaneously, sleeve valve 58 covers outlet 77 in tube 76. This discontinues the flow of high-pressure gas into the gas surge chamber 17 of the pilot valve section of the apparatus.

In operation, the cross-over fitting shown in FIGURE 2 is lowered into the casing 10 on the production tubing -to the elevation at which it is desired to inject gas into the tubing. Obviously, two or more of these or similar cross-over fittings may be installed at spaced points along the production conduit so that, if desired, retrievable kickoff valves can be installed at preselected elevations. The size of orifice 22 is then selected and threaded into the lower gas chamber head 63. The removable valve 24' is then either dropped or lowered by a wire line tool into position in the cross-over fitting, as shown. Gas is then injected into the gas conduit 21. After excess liquid is displaced out of the tubing by kick-ofi valves, as discussed previously, the gas passes through gas inlet 32 and the inlet gas port 62 into the inlet gas chamber 73. Gas leaves the chamber through outlet 77 and flows through tube 76 and orifice 22 into gas surge chamber 1717". When the pressure in the surge chamber becomes as great as the preset opening pressure of valve 44, the downward force on the valve member due to the compression spring 45 and the compressible fluid in the bellows 48 is overcome by the external gas pressure on the bellows, causing the valve member 44 to open surge chamber outlet 43 and admit the high-pressure gas into chamber 73. The rapid flow of gas into this chamber collapses the bellows 55 and moves the rod 56 downward, carrying slide valve 57 downward. This uncovers outlet port 65 and closes outlet '77. In this position of slide valve 57 and sleeve valve 58 the gas in chamber 78 can now flow through outlet port 65 and gas injection port 37 into the annular passage 38. This sudden increase in tubing pressure adjacent the gas valve causes the standing valve to close while a slug of gas enters the tubing and displaces the well fluids toward the surface.

The gas pressure inside chamber 73 slowly decreases as the gas vents through exhaust port 72. When the pressure declines to that which permits valve member 44 to close surge chamber outlet 43, the pressure inside the gas surge chamber through the orifice, building up the pressure in the chamber, well fluids are entering the lower end of the production tubing and flowing upward through the fluid inlet port 40 of the bypass fitting and displacing the previous slug of liquid and the intermediate gas slug upwardly in the production tubing toward the surface. The valve 57 continues to operate, i.e., open and close, as the pressure oscillates in the gas surge chamber, thereby intermittently injecting into the tubing at high frequency alternate slugs of gas and liquid. It can be seen that by stopping the flow of gas to the orifice in gas cham ber 17'--17", while gas is flowing from the surge chamber the operation of the valve is dependent on fewer variables.

The length of time the gas injection valve member 67 in the apparatus of FIGURE 1 remains closed during each cycle is a function of the flow rate through orifice 22 and the volume of surge chamber 1717". As pointed out previously, the valve remains closed until sufficient high-pressure gas enters the surge chamber through orifice 22 to compress bellows 48 and unseat valve 44 to start another cycle. The length of time the gas valve 67 remains open is controlled by the rate of gas flow from the surge chamber through the exhaust port. The volume of the surge chamber will be chosen to provide the proper range for the operation of the valve at the lift gas pressure and the head of the well fluids for a particular well. More precise adjustments and control of the open-closed periods for the main gas valve will be obtained by selection of the size of orifice 22 and exhaust port 72. As discussed earlier, the pressure inside the pilot valve bellows 48, as well as the characteristics of springs 45 and 69, also affect the valve cycles. Another element in the design of this apparatus which affects its operation is the force holding pilot valve 44 against outlet 43 owing to the ditferential pressure across the valve. The valve starts to open when its opening pressure is reached in the surge chamber. Gas flows into the gas chamber 73 where the exhaust port 72 restricts the flow from the chamber. This decreases the pressure drop across the pilot valve and enables the bellows 43 and spring 45 to compress further. The ultimate effect of this equalization of pressure across the valve is that the valve will not close until the pressure inside the surge chamber falls to a level substantially below that required to open the valve.

By closing the gas supply to orifice 22 during the time valve 44 is unseated and the pressure inside surge chamber 17-17" is venting, the eflect of flow rate through the orifice during this portion of the cycle is eliminated. If the outlet 77 were not closed and gas continued to enter the surge chamber while gas is exhausting through outlet 43, as it does in the apparatus described in my earlier application Serial No. 714,108, the gas injection valve would admit lift gas to the tubing for a period of time proportional to the sum of the flow capacities of port 72 and orifice 22. Thus, orifice 22 may be changed to alter the time the gas valve remains closed without affecting the length of the time it is open. Obviously, this simplifies the'setting of the valve to obtain the proper volume of gas slug in the liquid column. By shutting off the supply of gas to orifice 22 during the time the surge chamber is exhausting, the tendency of valve 44 to throttle is overcome. It can be seen that a condition might develop it this gas supply were not interrupted wherein the valve 44 would move to a partially closed position whereby flow through outlet 43 would be equal to the flow entering the surge chamber through orifice 22. This condition would enable gas to be admitted to the tubing continuously.

From the foregoing it can be seen that various modifications can be made in the gas lift apparatus disclosed. For example, the periods in the operating cycle can be varied by altering either the volume of the surge chamber or by varying the flow capacity of the passages. In the alternative, all of these variables can be changed. Also, the valve can be designed for use in the annulus between the casing and tubing, or it may be placed within the tubing as retrievable equipment in combination with a crossover device. This invention thus being susceptible to a wide variation of embodiments, should not be construed to be limited to those embodiments specifically described above. It should instead be construed to be limited only by the scope of the appended claims.

I claim:

1. A gas lift valve assembly comprising:

a main valve assembly including a valve member and a housing, said housing defining a fluid passage controlled by said member,

resilient means acting between said valve member and said housing for urging said valve member into closed position,

a fluid motor attached to said housing and adapted to open said valve member,

a fluid pressure-actuated pilot valve assembly attached to said housing and constructed and arranged so as to communicate with said motor to admit fluid to actuate said fluid motor,

means constructed and arranged so as to communicate with said valve member and said pilot valve to admit fluid to said pilot valve only when said valve member closes said fluid passage, said means including a pilot valve fluid conduit, and

an exhaust conduit communicating With said motor to lower fluid pressure therein and to close said pilot valve after said main valve assembly opens,

said fluid motor being operable to reciprocate said valve member, alternately closing said lift gas outlet port and said pilot valve fluid conduit.

2. The apparatus of claim 1 wherein the flow capacity of said exhaust conduit is less than that of said pilot valve.

3. The apparatus of claim 1 wherein said pilot valve opens when the pressure in said valve assembly reaches a preset level and closes when said pressure drops to a preset level below said opening pressure.

4. The apparatus of claim 1 wherein said fluid motor comprises a variable volume housing having a movable wall, said wall having means to engage and move said valve member in response to the pressure in said variable volume housing.

5. A gas lift valve assembly comprising:

a valve including a valve member and an associated housing,

upper and lower valve seats in said housing,

a lift gas inlet between said upper and lower valve seats, said valve member being constructed and arranged to seat on said upper and lower valve seats so that said upper and lower valve seats together with said housing define a chamber, so arranged that gas communicates with said chamber through said gas inlet,

a piston in said valve body in operative connection with said valve member,

resilient means urging said valve member against said upper seat,

a lift gas outlet in said valve body between said piston and said upper valve seat,

a pressure-actuated pilot valve attached to said valve body above said piston,

said pilot valve including a housing,

said pilot valve having a port in said housing in fluid communication with said valve body,

said pilot valve being arranged to close said port,

a restricted passage through said piston,

an operating gas inlet in said pilot valve housing,

a metering conduit constructed and arranged so as to communicate with said operating gas inlet and said lower valve seat in said valve body, and

means connecting said lift gas outlet to a well tubing.

6, Apparatus for gas lifting liquids from a well comprising:

a casing in said well,

a tubing in said casing,

a packer between said tubing and easing,

a Well fluid inlet in said tubing below said packer,

a lift gas inlet in said tubing above said packer,

a motor-operated gas valve connected to said lift gas inlet to control the flow of gas from said casing to said tubing,

a pilot valve in fluid communication with said motoroperated gas valve,

a housing enclosing said pilot valve,

said pilot valve being arranged to discharge gas from said housing to said gas valve motor when the pressure in said housing reaches a preset level,

a restricted gas vent between said gas valve motor and said tubing,

a metering gas inlet to said pilot valve housing,

said motor-operated gas valve being arranged to admit gas from said casing to said metering gas inlet when the flow of gas to said tubing is interrupted.

7. The apparatus of claim 6 wherein the volume of said pilot valve housing is substantially less than that of said casing above said packer and outside said tubing.

8. The apparatus of claim 6 wherein said vent between said motor and tubing is adapted to discharge gas from said motor at a rate below that which said pilot valve admits gas to said motor from said housing.

9. A retrievable gas lift valve assembly comprising:

a valve body having gas inlet and outlet ports,

a valve member in said valve body,

a fluid motor in operative connection with said valve member,

a housing attached tosaid valve body,

a fluid outlet in said housing in communication with said fluid motor,

a pressure-actuated pilot valve in said housing adapted to control the flow of fluid from said housing to said motor,

a vent between said motor and said valve body outlet,

a fluid inlet in said pilot valve housing,

a fluid conduit between said housing fluid inlet and said valve body,

said valve member being adapted to alternate the flow of gas between said housing fluid conduit and said valve body outlet as said pilot valve intermittently supplies fluid to said fluid motor,

means for latching said valve body to a well tubing,

and

a fishing neck on the top of said housing.

10. The apparatus of claim 9 wherein said fluid motor comprises a variable volume housing having a movable wall, said wall having means to engage and move said valve member in response to the pressure in said variable volume housing.

11. The apparatus of claim 9 wherein said pilot valve opens said housing outlet when the pressure in said housing reaches a preset level and closes said outlet when said pressure drops to a preset level below said opening pressure.

12. The apparatus of claim 9 wherein said fluid outlet in said housing has a flow capacity greater than said vent between said motor and said valve body outlet.

13. An apparatus for gas lifting liquid from a well comprising:

a tubing in said well,

a valve anchoring device near the lower end of said tubing,

a gas conduit extending down said well to said anchoring device,

a fluid bypass longitudinally through said anchoring device,

a radial opening through said anchoring device to admit gas from said gas conduit into said tubing,

a passage between said bypass and said tubing,

a gas valve body adapted for latching engagement in said anchoring device,

a gas inlet port in said valve body positioned for fluid communication with said radial opening,

a gas outlet port in said valve body positioned for fluid communication with said passage between said bypass and said tubing,

a valve member in said valve body,

a fluid motor in operative engagement with said valve member,

a housing attached to said fluid motor,

a fluid passage between said housing and said fluid motor,

a pressure-actuated pilot valve in said housing adapted to control the flow of fluid from said housing to said fluid motor,

a vent between said fluid motor and said tubing above said fluid bypass,

a fluid inlet in said housing, and

a conduit between said housing inlet and said valve body,

said valve member being adapted to alternate the flow of gas from said valve body between said housing and said tubing as said pilot valve intermittently admits fluid to said motor.

14. The apparatus of claim 13 wherein said fluid passage between said housing and said fluid motor has a flow capacity greater than said vent between said fluid motor and said tubing.

15. The apparatus of claim 13 wherein said pilot valve admits fluid from said housing to said fluid motor when the pressure in said housing reaches a preset level and stops said flow of fluid when said pressure drops to a preset level below said opening pressure.

16. The apparatus of claim 13 wherein said fluid motor comprises a variable volume housing having a movable wall, said wall having means to engage and move said valve member in response to the pressure in said variable volume housing.

References Cited in the file of this patent UNITED STATES PATENTS 2,179,226 Bryan Nov. 7, 1939 2,184,636 Crickmer Dec. 26, 1939 2,342,301 Peters Feb. 22, 1944 2,391,542 Benard Dec. 25, 1945 2,446,680 Walton Aug. 10, 1948 2,573,110 Robinson Oct. 30, 1951 2,594,831 Walton Apr. 29, 1952 2,620,741 Garrett Dec. 9, 1952 2,642,811 Fletcher June 23, 1953 2,642,812 Robinson June 23, 1953 3,010,406 Vincent Nov. 28, 1961 3,016,844 Vincent Jan. 16, 1962 

1. A GAS LIFT VALVE ASSEMBLY COMPRISING: A MAIN VALVE ASSEMBLY INCLUDING A VALVE MEMBER AND A HOUSING, SAID HOUSING DEFINING A FLUID PASSAGE CONTROLLED BY SAID MEMBER, RESILIENT MEANS ACTING BETWEEN SAID VALVE MEMBER AND SAID HOUSING FOR URGING SAID VALVE MEMBER INTO CLOSED POSITION, A FLUID MOTOR ATTACHED TO SAID HOUSING AND ADAPTED TO OPEN SAID VALVE MEMBER, A FLUID PRESSURE-ACTUATED PILOT VALVE ASSEMBLY ATTACHED TO SAID HOUSING AND CONSTRUCTED AND ARRANGED SO AS TO COMMUNICATE WITH SAID MOTOR TO ADMIT FLUID TO ACTUATE SAID FLUID MOTOR, MEANS CONSTRUCTED AND ARRANGED SO AS TO COMMUNICATE WITH SAID VALVE MEMBER AND SAID PILOT VALVE TO ADMIT FLUID TO SAID PILOT VALVE ONLY WHEN SAID VALVE MEMBER CLOSES SAID FLUID PASSAGE, SAID MEANS INCLUDING A PILOT VALVE FLUID CONDUIT, AND AN EXHAUST CONDUIT COMMUNICATING WITH SAID MOTOR TO LOWER FLUID PRESSURE THEREIN AND TO CLOSE SAID PILOT VALVE AFTER SAID MAIN VALVE ASSEMBLY OPENS, SAID FLUID MOTOR BEING OPERABLE TO RECIPROCATE SAID VALVE MEMBER, ALTERNATELY CLOSING SAID LIFT GAS OUTLET PORT AND SAID PILOT VALVE FLUID CONDUIT. 